User-Centered Mobile Applications for Stroke Survivors (MAPPS): A Mixed-Methods Study of Patient Preferences

OBJECTIVE

Investigate stroke survivors' (SS) preferences for a hypothetical mHealth app for post-stroke care and to study the influence of demographic variables on these preferences.

DESIGN

Mixed-methods, sequential, observational study.

SETTING

Focus groups (phase 1) were conducted to identify SS perceptions and knowledge of mHealth applications (apps). Using grounded theory approach, recurring themes were identified. A multiple-choice questionnaire of 5 desired app features was generated using these themes and mailed to SS (national survey, phase 2). SS' demographics and perceived usefulness (yes/no) for each feature were recorded. In-person usability testing (phase 3) was conducted to identify areas of improvement in user interfaces of existing apps. Summative telephone interviews (phase 4) were conducted for final impressions supplementary to national survey.

PARTICIPANTS

SS aged >18 years recruited from study hospital, national stroke association database, stroke support and advocacy groups. Non-English speakers and those unable to communicate were excluded.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

(1) Percentage of SS (phase 2) identifying proposed app features to be useful. (2) Influence of age, sex, race, education, and time since stroke on perceived usefulness.

RESULTS

Ninety-six SS participated in focus groups. High cost, complexity, and lack of technical support were identified as barriers to adoption of mHealth apps. In the national survey (n=1194), ability to track fitness and diet (84%) and communication (70%) were the most and least useful features, respectively. Perceived usefulness was higher among younger SS (P<.001 to .006) and SS of color (African American and Hispanic) (ORs 1.73-4.41). Simple design and accommodation for neurologic deficits were main recommendations from usability testing.

CONCLUSIONS

SS are willing to adopt mHealth apps that are free of cost and provide technical support. Apps for SS should perform multiple tasks and be of simple design. Greater interest for the app's features among SS of color may provide opportunities to address health inequities.

Abstract TP73: User-centered Mobile Applications For Stroke Survivors (MAPPS): A National Survey Of Patient Preferences

Introduction: Existing mobile health (mHealth) smartphone applications (apps) for stroke survivors (SS) are poorly adopted. Little is known about SS’ perceptions and preferences for such apps. We conducted a national survey of SS' preferences for a hypothetical mHealth app for post-stroke care, and studied the influence of demographic variables on these preferences.

Methods: Focus groups were conducted to identify SS perceptions and knowledge of mHealth apps. Using a grounded theory approach, recurring themes were identified. A multiple-choice questionnaire of five desired app features was generated using the themes. The national survey was mailed to SS (n= 11, 720) across the United States. Survey responses, demographic variables (age, sex, race), education, and time-since-stroke were recorded.

Results: Ninety-six SS participated in focus groups. High cost, complexity of use, and lack of technical support were identified as possible impediments to adoption of mHealth apps. In the national survey (n=1,194, 10% response), ability to track fitness and diet (84%) and communicating with others (70%) emerged as the most and least useful app features, respectively. African-American and Hispanic SS found the app's features (all five) more useful compared to White SS (ORs 1.73 to 4.41). Stroke survivors with stroke greater than ten years ago deemed the features less useful compared to SS with stroke within one year (ORs 0.01 to 0.78). Perceived usefulness was higher in women ( P = 0.04 to <0.001) and younger SS ( P= 0.006 to <0.001) only in univariate analysis.

Conclusion: Successful adoption of mHealth apps among SS will likely depend on app development that is driven by patient preferences and demographics. A patient-centered app may help address health disparities in post-stroke care.

Prior employment status and obesity do not predict post-stroke fatigue

Aim: To investigate whether prior employment status or obesity pose as risk factors for post stroke fatigue in patients following an ischemic stroke. Materials & methods: A total of 121 patients with a confirmed diagnosis of ischemic stroke in the past 3 years were enrolled into the study. Post-stroke fatigue (PSF) was assessed using the fatigue assessment scale (no PSF ≤21, PSF 22–50). Patients were then identified based on their employment status (previously worked) or obesity (BMI) and compared with the presence of PSF. Results: A Fisher’s exact test was applied to determine the association between PSF and obesity (p = 1.000). A Fisher’s exact test was applied to show the association between PSF and employment status (p = 0.384). In logistic regression, employment status did not independently predict dichotomized fatigue assessment scale (adjusted odds ratio 1.34, 95% CI: 0.51–3.50, p = 0.557). Conclusion: Previous employment status and obesity did not independently predict PSF in an urban, minority community.

Seven-Year Experience From the National Institute of Neurological Disorders and Stroke-Supported Network for Excellence in Neuroscience Clinical Trials

Importance

One major advantage of developing large, federally funded networks for clinical research in neurology is the ability to have a trial-ready network that can efficiently conduct scientifically rigorous projects to improve the health of people with neurologic disorders.

Observations

National Institute of Neurological Disorders and Stroke Network for Excellence in Neuroscience Clinical Trials (NeuroNEXT) was established in 2011 and renewed in 2018 with the goal of being an efficient network to test between 5 and 7 promising new agents in phase II clinical trials. A clinical coordinating center, data coordinating center, and 25 sites were competitively chosen. Common infrastructure was developed to accelerate timelines for clinical trials, including central institutional review board (a first for the National Institute of Neurological Disorders and Stroke), master clinical trial agreements, the use of common data elements, and experienced research sites and coordination centers. During the first 7 years, the network exceeded the goal of conducting 5 to 7 studies, with 9 funded. High interest was evident by receipt of 148 initial applications for potential studies in various neurologic disorders. Across the first 8 studies (the ninth study was funded at end of initial funding period), the central institutional review board approved the initial protocol in a mean (SD) of 59 (21) days, and additional sites were added a mean (SD) of 22 (18) days after submission. The median time from central institutional review board approval to first site activation was 47.5 days (mean, 102.1; range, 1-282) and from first site activation to first participant consent was 27 days (mean, 37.5; range, 0-96). The median time for database readiness was 3.5 months (mean, 4.0; range, 0-8) from funding receipt. In the 4 completed studies, enrollment met or exceeded expectations with 96% overall data accuracy across all sites. Nine peer-reviewed manuscripts were published, and 22 oral presentations or posters and 9 invited presentations were given at regional, national, and international meetings.

Conclusions and Relevance

NeuroNEXT initiated 8 studies, successfully enrolled participants at or ahead of schedule, collected high-quality data, published primary results in high-impact journals, and provided mentorship, expert statistical, and trial management support to several new investigators. Partnerships were successfully created between government, academia, industry, foundations, and patient advocacy groups. Clinical trial consortia can efficiently and successfully address a range of important neurologic research and therapeutic questions.

Binding properties to nicotinic acetylcholine receptors can explain differential toxicity of neonicotinoid insecticides in Chironomidae

Neonicotinoids are neuroactive insecticides commonly detected in freshwater ecosystems. Recent studies have indicated that these compounds are markedly toxic to Chironomidae, a widespread family of ecologically important aquatic insects. However, despite their sensitivity, the pharmacological mechanisms driving neonicotinoid toxicity have yet to be characterized in these insect species. Here, we used a combination of saturation and competition binding studies to characterize neonicotinoid binding properties to nicotinic acetylcholine receptors (nAChR) in two different Chironomidae (Chironomus riparius and Chironomus dilutus) at two different life stages (larval and adult). Using radiolabeled imidacloprid ([³H]-IMI), we characterized and compared receptor density (B_max), imidacloprid binding affinity (K_D), and receptor binding affinity (K_i) to three different neonicotinoid competitors (imidacloprid, clothianidin, and thiamethoxam). We then compared receptor density and binding affinity parameters derived for Chironomidae to data previously generated for other dipterans and agricultural pests. We found that there were limited differences in neonicotinoid binding between C. riparius and C. dilutus, with both organisms demonstrating high affinities for imidacloprid (K_D = 0.22-0.87 nM) and high receptor densities (B_max = 0.92-6.53 pmol/mg). However, there were significant differences between life-stages, with larvae expressing higher densities of nicotinic acetylcholine receptors and higher imidacloprid affinities than adults. Moreover, there were compound-specific differences in receptor affinity, with larval stages displaying relative affinities (K_i) that generally correlated with acute neonicotinoid toxicity (e.g. clothianidin ≥ imidacloprid >>> thiamethoxam). Finally, compared to other dipterans and agricultural pests, Chironomidae display very high densities of high affinity nicotinic acetylcholine receptors, which likely contribute to their sensitivity. Results indicated that receptor-level differences in neonicotinoid binding may be responsible for ecotoxicological differences amongst distinct insect species, and they likely play a role in life stage-, and compound-level toxicity differences previously observed for Chironomidae. Overall, this study highlights the value of understanding the toxicological mechanisms of action of neonicotinoids in sensitive, non-target aquatic insects, to better predict adverse effects associated with unintentional neonicotinoid exposure.

Abstract TP297: Predictors of Acute Ischemic Stroke in Patients Presenting to the Emergency Department With Dizziness, Imbalance, and Vertigo

Objectives: To identify predictors of acute ischemic stroke (AIS) among patients presenting to the Emergency Department (ED) with dizziness, imbalance, or vertigo (DIV) based on demographic and clinical characteristics.

Methods: We identified patients admitted to the hospital after presenting to the ED with DIV from the Statewide Planning and Research Cooperative System database of New York from 2010 through 2014. ICD-9-CM codes were used to identify patient's clinical characteristics. Demographic and clinical characteristics were systematically collected. Multivariable logistic regression was used to determine predictors of a discharge diagnosis of AIS.

Results: Among 77,993 patients with DIV, 3,857 (4.9%) had a discharge diagnosis of AIS. Admission presentation of imbalance (Odd ratio [OR] 1.64 95% confidence interval [CI] 1.51-1.77 p<0.001), African-American race (OR 1.15, 95% CI 1.05-1.25, p=0.002), history of hypertension (OR 1.60, 95% CI 1.49-1.72, p<0.001), diabetes mellitus (OR 1.39, 95% CI 1.29-1.49, p<0.001), hypercholesterolemia (OR 1.52, 95% CI 1.42-1.62, p<0.001), tobacco use (OR 1.70, 95% CI 1.53-1.88, p<0.001), atrial fibrillation (OR 1.41, 95% CI 1.28-1.56, p<0.001), and prior AIS due to extracranial artery atherosclerosis (OR 4.47, 95% CI 4.00-5.01, p<0.001) were each positively associated with an AIS diagnosis independently. Factors negatively associated with an AIS discharge diagnosis included: admission presentation of vertigo (OR 0.56, 95% CI 0.41-0.75, p<0.001), female sex (OR 0.64, 95% CI 0.60-0.69, p<0.001), age>81 (OR 0.86, 95% CI 0.77-0.96, p=0.01), history of anemia (OR 0.65, 95% CI 0.58-0.73, p<0.001), coronary artery disease (OR 0.84, 95% CI 0.78-0.91, p<0.001), asthma (OR 0.68, 95% CI 0.59-0.76, p<0.001), depressive disorders (OR 0.74, 95% CI 0.64-0.84, p<0.001), and anxiety disorders (OR 0.70, 95% CI 0.59-0.82, p<0.001).

Conclusions: Multiple potential positive and negative predictive AIS risk factors were identified. Combining with currently available centrally-caused dizziness prediction tools, these newly identified factors could provide more accurate AIS risk stratifying method for DIV patients.

Ischemic Stroke Predictors in Patients Presenting with Dizziness, Imbalance, and Vertigo

OBJECTS

To identify predictors of acute ischemic stroke (AIS) among patients presenting to the Emergency Department (ED) with dizziness, imbalance, or vertigo (DIV) based on demographic and clinical characteristics.

METHODS

We identified patients admitted to the hospital after presenting to the ED with DIV from the Statewide Planning and Research Cooperative System database of New York from 2010 to 2014. Demographic and clinical characteristics were systematically collected. Multivariable logistic regression was used to determine predictors of a discharge diagnosis of AIS.

RESULTS

Among 77,993 patients with DIV, 3857 (4.9%) had a discharge diagnosis of AIS. Admission presentation of imbalance, African-American race, history of hypertension, diabetes mellitus, hypercholesterolemia, tobacco use, atrial fibrillation, and prior AIS due to extracranial artery atherosclerosis were each positively associated with an AIS diagnosis independently. Factors negatively associated with an AIS discharge diagnosis included: admission presentation of vertigo, female sex, age > 81, history of anemia, coronary artery disease, asthma, depressive disorders, and anxiety disorders.

CONCLUSIONS

Multiple potential positive and negative predictive AIS risk factors were identified. Combining with currently available centrally-caused dizziness prediction tools, these newly identified factors could provide more accurate AIS risk stratifying method for DIV patients.

Abstract TP159: Beta Blockers Do Not Increase the Risk of Post-Stroke Depression in a Predominantly Afro-Caribbean Population

Background: Depression is one of the most common neuropsychiatric disorders among ischemic stroke survivors, affecting up to 50%. Beta-blockers (BB) are commonly prescribed for stroke patients and the evidence for an association between BB use and depression is mixed. We explored this relationship in an urban, predominantly Afro-Caribbean stroke cohort.

Hypothesis: The use of BB will be associated with an increase in frequency and severity of post-stroke depression.

Methods: Observational, cross-sectional, prospective study of eligible non-demented patients with ischemic stroke in the past 3 years and without a history of major depression. Subjects were recruited from the inpatient stroke unit, outpatient stroke clinics (including at Kings County Hospital), and inpatient rehabilitation unit at SUNY Downstate Medical Center. Demographics, medical history, and current medications were recorded from medical records and patient interviews. Depression was assessed using Beck’s Depression Inventory (BDI). For bivariate analysis, the Mann-Whitney test was used to associate BB usage with BDI score. For multiple regression analysis, a general linear model was constructed, with square-root (BDI score) as the dependent variable. Covariates were history of myocardial infarction and/or coronary artery disease, NIH Stroke Scale, and age.

Results: Of 83 subjects enrolled, 76 (91%) were Afro-Caribbean, 47 (56%) were female, and mean age was 66.9 (SD±12.7) yrs. Median (Q1,Q3) BDI score was 7 (3,10) for BB users (N=37), 5 (3,9) for no BB use (N=46) ( p =0.275). Controlling for covariates (sample n=83), the difference remained non-significant ( p =0.909). There were 10 patients with BDI scores over 13, indicating their depression was worse than minimal, and of these, 6 were on BB.

Conclusion: BB use was not associated with a significant increase in the severity or frequency of depression in this urban, predominantly Afro-Caribbean post-stroke population.

Abstract WP173: Women Have More Severe Post-Stroke Fatigue Than Men

Background: Gender-related differences in stroke are issues of increasing interest. Post- stroke fatigue (PSF) is a frequently reported symptom affecting stroke survivors and is a predictor for death and increased disability.

Aims: To evaluate gender differences and predictors in PSF in an urban predominantly minority cohort.

Methods: Two-center, IRB approved, prospective study serving primarily African/Caribbean Americans. Eligible patients included ischemic stroke within 3 years. Aphasia, dementia or pre-existing depression were exclusions. PSF was assessed by Fatigue Assessment Score (FAS); depression by the Beck Depression Inventory (BDI). Primary outcome was FAS log-transformed due to its skewed distribution. Multiple linear regression determined gender differences in PSF, adjusted for prior stroke, diabetes (DM), atrial fibrillation (AF), hypertension (HTN) and the following dichotomized predictors: stroke severity (NIHSS >2), BDI score (≥11), age (≥55), and time from stroke onset (>30 days). First-order interactions between gender and other predictors were investigated. Chi square test was used to test for gender differences in the distribution of the other categorical predictors. P<0.05 was considered significant.

Results: 150 patients, mean age 66 years (SD=13, range 30-93); 82 (55%) women. Higher rates of prior stroke (44% vs 28%, p=0.04) and AF (15% vs 4%, p=0.04) were present in women than in men. No gender differences were observed for the other predictors. We found that female gender was associated with 18% (95% CI: 4%-33%, p=0.009) higher levels of PSF, adjusted for other predictors. Two other predictors were associated with greater PSF severity: BDI ≥11 with 34% (95% CI: 14%-57%, p=0.0005) and NIHSS>2 with 14% (95% CI: 0.3%-29%, p=0.045) increase in the PSF. However, HTN was associated with 24% (95% CI: 9%-37%, p=0.004) decreased PSF severity. The 8 included predictors explained 30% of the variability in the PSF severity.

Conclusions: In our urban, predominately minority cohort, women had more severe PSF than men. As the basis for PSF remains to be elucidated, our data suggest that gender-specific factors may modulate the magnitude of PSF. The protective effect of HTN on PSF severity is unclear and deserves further study.

Abstract WP379: What Informal Caregivers Want in a Mobile Application: Evidence-based Interventions

Background: Nurses play a critical role supporting informal caregivers of stroke patients and thus need evidence of best, client centered interventions. Although there is a growing literature evaluating interventions, there is a paucity of research that begins with and engages caregiver stakeholders in identifying interventions, especially with the use of mobile health technologies.

Research Question: What do stroke survivor informal caregivers want in a mobile application?

Methods: A cross-sectional, descriptive study of informal stroke caregivers from a national convenience sample of the National Stroke Association database was conducted using a 17-item survey mailed to stroke survivors asking their caregivers to identify useful educational content/knowledge and resources. Descriptive statistics and logistic regressions were performed to analyze data and examine the relationships among demographic variables and caregiver needs.

Results: Of 396 respondents, 76% were female (mean age 59 years +/-13.3; range 20-99); 53%, Caucasian; 24%, African-American; 11%, Hispanic/Latino. A majority (76% to 81%) of respondents wanted information about scheduling tasks and appointments, local resources, internet resources, fitness and diet tracking, and tools for communication with the stroke survivor; 81% of respondents wanted information about support groups. Ninety-six percent of caregivers owned a cell phone; 60% of which were smart phones. As age increased, reported usefulness of the app decreased (p = 0.05). There were no significant differences related to gender, race/ethnicity, or whether or not the caregiver owned a smartphone.

Conclusion: Consistent responses across population groups suggest that nurses can use the findings to develop mobile applications for smartphone users, to use the content to develop written resource guides for discharge planning, and to customize care plans to support stroke caregivers with and without smartphones. Discharge plans for informal caregivers should include specific information about stroke survivor services, how to arrange healthcare appointments, educational materials about strokes, and guidance in best methods for communicating with the stroke survivor.

Abstract TP153: Post Stroke Fatigue and Depression Predict Lower Health Related Quality of Life in Stroke Patients

Background and Purpose: Post stroke fatigue (PSF) is a common and debilitating condition that can last months or even years. Although the relationship between PSF and Health Related Quality of Life (HRQoL) has been studied, the results have been largely inconclusive and not previously reported in a minority cohort.

Hypothesis: Higher levels of PSF and Post Stroke Depression (PSD), will predict lower levels of HRQoL in African/Caribbean Blacks.

Methods: Prospective, cross-sectional, observational study approved by the IRB. Patients ≥ 18 years old with a stroke in the past 3 years were enrolled. Standardized questionnaires were administered to assess the patients’ levels of PSF [Fatigue Assessment Scale (FAS)], HRQoL [Short Form-36 (SF-36)], and PSD [Beck’s Depression Inventory (BDI)]. Stroke related disability was assessed by modified Rankin Scale (mRS). Responses to the SF-36 were weighted and then averaged in accordance to standard practices. FAS, BDI, and mRS scores were dichotomized and adjusted for gender. A multiple linear regression model was constructed for the HRQoL overall score. The dichotomized FAS, BDI, and mRS scores, age and gender were considered as predictors.

Results: Of 100 patients enrolled (55% female), mean age = 66.7 years ± 12.8; 93% African or Caribbean American, 86% with hypertension, 53% with diabetes, and 37% with a family history of stroke/TIA. The prevalence of stroke related disability (mRS ≥ 2) was 63%, PSF (FAS≥22) was 51%, PSD (BDI ≥11) was 24%. Both PSF and PSD was seen in 20%. The cohort’s mean SF-36 score was 51.6 ± 21.1. BDI <11 was associated with a score 9.5 units higher on the SF-36 (95% CI: 2.3-16.8, p =0.01) than BDI ≥ 11; mRS <2 was associated with 19.8 units higher score on the SF-36 (95%CI: 13.7-25.8, p<0.0001) than mRS≥2. FAS score<22 was associated with 15.0 higher HRQoL score (95%CI: 8.9-21.1, p <0.0001) than FAS≥ 22. The analysis was adjusted for gender ( p =0.10), while age ( p =0.29) was not included. BDI, mRS, FAS, and gender accounted for 56% of the variability in the HRQoL score.

Conclusion: Our results suggest that both PSF and PSD are significantly correlated with a lower HRQoL. In this minority cohort, over half of post-stroke HRQoL is attributed to depression, disability, fatigue, and female gender.

Abstract TP312: Developing a Mobile Application for Stroke Informal Caregivers

Background: Following stroke, many survivors require assistance with activities of daily living from untrained individuals. These informal caregivers assume multiple new responsibilities, which can generate stress, especially when their own needs are inadequately addressed during a patient’s recovery.

Methods: A nationwide survey mailed to 11,720 stroke survivors through the National Stroke Association with a cover letter asking them to give the IRB approved informed consent and survey to their informal caregiver, if applicable. The 17 question survey asked caregivers about demographics, if they own a cell/smart phone, and the caregiver’s opinion about what resources in a mobile app (if any) would be useful – namely: 1) scheduling multiple tasks, 2) finding information about stroke resources, 3) finding local resources, 4) tracking fitness and diet, and 5) communication with their stroke survivor. The survey was developed using focus groups in 2 states. For all questions logistic regression determined if there were racial, gender, or age disparities.

Results: 396 stroke caregivers [(299 (76%) female, 96 (24%) African-American, 42 (11%) Hispanic/Latino, and 210 (53%) Caucasian], aged 20-99 years (mean 59.5 ± 13.3) returned surveys; 96% owned a cell phone; 60% of all caregivers owned a smart phone. Caregivers in this sample reported features of the app to be important including: doctor/rehab appointments (80%, 95% CI, 76-84%), links to trustworthy medical information (84%, 95% CI 80-87%), stroke support groups in my area (81%, 95% CI 77-85%), exercises (76%, 95% CI 71-80%), and a touch screen with useful phrases (76%, 95% CI 71-80%). When examining the utility of the 5 app resources (outlined above), Latino (88%-74%) and African-American (84%-77%) caregivers reported the highest rate of usefulness across the 5 aspects). As age increased, the caregivers’ reporting of mobile app usefulness decreased ( p < 0.05). However, in the oldest group (63+), 67-79% of caregivers reported that all 5 resources would be useful in a mobile app.

Conclusions: Implementation of a mobile app unique to stroke caregivers with resources is desired by this diverse, national sample of informal caregivers and holds potential to alleviate stress and improve patient’s recovery.

Impact of mental health training on village health workers regarding clinical depression in rural India

Village health worker (VHW) programs are known to be effective means of promoting health of communities. Comprehensive rural health project in India recently trained VHWs to identify, refer, and help people with mental health issues. This study evaluated knowledge, attitude, and behavior of VHWs regarding depression. Cluster sampling was used including all 36 VHWs trained in mental health. Among these, 24 were available and willing to participate in the study. Five FGDs were conducted among 24 VHWs, and the results were analyzed qualitatively. Four out of five groups were able to diagnose the presented case correctly as depression. VHWs were able to identify many symptoms and to suggest management options for depression. They showed supportive and empathetic attitudes towards depressed patients. VHWs are likely to be useful at identifying and assisting people with depression in the communities with lack of adequate resources provided they receive ongoing training and supervision.

Effects of ρ-Da1a a peptidic α(1) (A) -adrenoceptor antagonist in human isolated prostatic adenoma and anaesthetized rats

BACKGROUND AND PURPOSE

ρ-Da1a, a 65 amino-acid peptide, has subnanomolar affinity and high selectivity for the human α(1) (A) -adrenoceptor subtype. The purpose of this study was to characterize the pharmacological effects of ρ-Da1a on prostatic function, both in vivo and in vitro.

EXPERIMENTAL APPROACH

ρ-Da1a was tested as an antagonist of adrenaline-induced effects on COS cells transfected with the human α(1) (A) -adrenoceptor as well as on human isolated prostatic adenoma obtained from patients suffering from benign prostatic hyperplasia. Moreover, we compared the effects of ρ-Da1a and tamsulosin on phenylephrine (PHE)-induced increases in intra-urethral (IUP) and arterial pressures (AP) in anaesthetized rats, following i.v. or p.o. administration.

KEY RESULTS

On COS cells expressing human α(1) (A) -adrenoceptors and on human prostatic strips, ρ-Da1a inhibited adrenaline- and noradrenaline-induced effects. In anaesthetized rats, ρ-Da1a and tamsulosin administered i.v. 30 min before PHE significantly antagonized the effects of PHE on IUP. The pK(B) values for tamsulosin and ρ-Da1a for this effect were similar. With regards to AP, ρ-Da1a only reduced the effect of PHE on AP at the lowest dose tested (10 μg·kg(-1) ), whereas tamsulosin significantly reduced PHE effects at doses between 10 and 150 μg·kg(-1) .

CONCLUSIONS AND IMPLICATIONS

ρ-Da1a exhibited a relevant effect on IUP and a small effect on AP. In contrast, tamsulosin antagonized the effects of PHE on both IUP and AP. We conclude that ρ-Da1a is more uroselective than tamsulosin. ρ-Da1a is the most selective peptidic antagonist for α(1A) -adenoceptors identified to date and could be a new treatment for various urological diseases.

Identification, structural and pharmacological characterization of τ-CnVA, a conopeptide that selectively interacts with somatostatin sst3 receptor

Conopeptides are a diverse array of small linear and reticulated peptides that interact with high potency and selectivity with a large diversity of receptors and ion channels. They are used by cone snails for prey capture or defense. Recent advances in venom gland transcriptomic and venom peptidomic/proteomic technologies combined with bioactivity screening approaches lead to the identification of new toxins with original pharmacological profiles. Here, from transcriptomic/proteomic analyses of the Conus consors cone snail, we identified a new conopeptide called τ-CnVA, which displays the typical cysteine framework V of the T1-conotoxin superfamily. This peptide was chemically synthesized and its three-dimensional structure was solved by NMR analysis and compared to that of TxVA belonging to the same family, revealing very few common structural features apart a common orientation of the intercysteine loop. Because of the lack of a clear biological function associated with the T-conotoxin family, τ-CnVA was screened against more than fifty different ion channels and receptors, highlighting its capacity to interact selectively with the somatostatine sst3 receptor. Pharmacological and functional studies show that τ-CnVA displays a micromolar (Ki of 1.5μM) antagonist property for the sst3 receptor, being currently the only known toxin to interact with this GPCR subfamily.

Isolation and pharmacological characterization of AdTx1, a natural peptide displaying specific insurmountable antagonism of the alpha1A-adrenoceptor

BACKGROUND AND PURPOSE

Venoms are a rich source of ligands for ion channels, but very little is known about their capacity to modulate G-protein coupled receptor (GPCR) activity. We developed a strategy to identify novel toxins targeting GPCRs.

EXPERIMENTAL APPROACH

We studied the interactions of mamba venom fractions with alpha(1)-adrenoceptors in binding experiments with (3)H-prazosin. The active peptide (AdTx1) was sequenced by Edman degradation and mass spectrometry fragmentation. Its synthetic homologue was pharmacologically characterized by binding experiments using cloned receptors and by functional experiments on rabbit isolated prostatic smooth muscle.

KEY RESULTS

AdTx1, a 65 amino-acid peptide stabilized by four disulphide bridges, belongs to the three-finger-fold peptide family. It has subnanomolar affinity (K(i)= 0.35 nM) and high specificity for the human alpha(1A)-adrenoceptor subtype. We showed high selectivity and affinity (K(d)= 0.6 nM) of radio-labelled AdTx1 in direct binding experiments and revealed a slow association constant (k(on)= 6 x 10(6).M(-1).min(-1)) with an unusually stable alpha(1A)-adrenoceptor/AdTx1 complex (t(1/2diss)= 3.6 h). AdTx1 displayed potent insurmountable antagonism of phenylephrine's actions in vitro (rabbit isolated prostatic muscle) at concentrations of 10 to 100 nM.

CONCLUSIONS AND IMPLICATIONS

AdTx1 is the most specific and selective peptide inhibitor for the alpha(1A)-adrenoceptor identified to date. It displays insurmountable antagonism, acting as a potent relaxant of smooth muscle. Its peptidic nature can be exploited to develop new tools, as a radio-labelled-AdTx1 or a fluoro-labelled-AdTx1. Identification of AdTx1 thus offers new perspectives for developing new drugs for treating benign prostatic hyperplasia.

Solution structure of two insect-specific spider toxins and their pharmacological interaction with the insect voltage-gated Na+ channel

Delta-paluIT1 and delta-paluIT2 are toxins purified from the venom of the spider Paracoelotes luctuosus. Similar in sequence to mu-agatoxins from Agelenopsis aperta, their pharmacological target is the voltage-gated insect sodium channel, of which they alter the inactivation properties in a way similar to alpha-scorpion toxins, but they bind on site 4 in a way similar to beta-scorpion toxins. We determined the solution structure of the two toxins by use of two-dimensional nuclear magnetic resonance (NMR) techniques followed by distance geometry and molecular dynamics. The structures of delta-paluIT1 and delta-paluIT2 belong to the inhibitory cystine knot structural family, i.e. a compact disulfide-bonded core from which four loops emerge. Delta-paluIT1 and delta-paluIT2 contain respectively two- and three-stranded anti-parallel beta-sheets as unique secondary structure. We compare the structure and the electrostatic anisotropy of those peptides to other sodium and calcium channel toxins, analyze the topological juxtaposition of key functional residues, and conclude that the recognition of insect voltage-gated sodium channels by these toxins involves the beta-sheet, in addition to loops I and IV. Besides the position of culprit residues on the molecular surface, difference in dipolar moment orientation is another determinant of receptor binding and biological activity differences. We also demonstrate by electrophysiological experiments on the cloned insect voltage-gated sodium channel, para, heterologuously co-expressed with the tipE subunit in Xenopus laevis oocytes, that delta-paluIT1 and delta-paluIT2 procure an increase of Na+ current. delta-PaluIT1-OH seems to have less effect when the same concentrations are used.

A new omega-conotoxin that targets N-type voltage-sensitive calcium channels with unusual specificity

A new specific voltage-sensitive calcium channel (VSCC) blocker has been isolated from the venom of the fish-hunting cone snail Conus consors. This peptide, named omega-Ctx CNVIIA, consists of 27 amino acid residues folded by 3 disulfide bridges. Interestingly, loop 4, which is supposed to be crucial for selectivity, shows an unusual sequence (SSSKGR). The synthesis of the linear peptide was performed using the Fmoc strategy, and the correct folding was achieved in the presence of guanidinium chloride, potassium buffer, and reduced/oxidized glutathione at 4 degrees C for 3 days. Both synthetic and native toxin caused an intense shaking activity, characteristic of omega-conotoxins targeting N-type VSCC when injected intracerebroventricularly to mice. Binding studies on rat brain synaptosomes revealed that the radioiodinated omega-Ctx CNVIIA specifically and reversibly binds to high-affinity sites with a K(d) of 36.3 pM. Its binding is competitive with omega-Ctx MVIIA at low concentration (K(i) = 2 pM). Moreover, omega-Ctx CNVIIA exhibits a clear selectivity for N-type VSCCs versus P/Q-type VSCCs targeted respectively by radioiodinated omega-Ctx GVIA and omega-Ctx MVIIC. Although omega-Ctx CNVIIA clearly blocked N-type Ca(2+) current in chromaffin cells, this toxin did not inhibit acetylcholine release evoked by nerve stimuli at the frog neuromuscular junction, in marked contrast to omega-Ctx GVIA. omega-Ctx CNVIIA thus represents a new selective tool for blocking N-type VSCC that displays a unique pharmacological profile and highlights the diversity of voltage-sensitive Ca(2+) channels in the animal kingdom.

Effect of depolarization on binding kinetics of scorpion alpha-toxin highlights conformational changes of rat brain sodium channels

Binding of scorpion alpha-toxins to receptor site 3 on voltage-gated sodium channels inhibits sodium current inactivation and is voltage-dependent. To reveal the direct effect of depolarization, we analyzed binding kinetics of the alpha-toxin Lqh-II (from Leiurus quinquestriatus hebraeus) to rat brain synaptosomes and effects on rat brain II (rBII) channels expressed in mammalian cells. Our results indicated that the 33-fold decrease in toxin affinity for depolarized (0 mV, 90 mM [K(+)](out), K(d) = 5.85 +/- 0.5 nM) versus polarized (-55 mV, 5 mM [K(+)](out), K(d) = 0.18 +/- 0.04 nM) synaptosomes at steady state results from a 48-fold reduction in the association rate (k(on) at 5 mM [K(+)] = (12.0 +/- 4) x 10(6) M(-1) s(-1) and (0.25 +/- 0.03) x 10(6) M(-1) s(-1) at 90 mM [K(+)](out)) with nearly no change in the dissociation rate. Electrophysiological analyses of rBII channels expressed in mammalian cells revealed that approximately 75% and 40% of rBII occupied fast- and slow-inactivated states, respectively, at resting membrane potential of synaptosomes (-55 mV), and Lqh-II markedly increased the steady-state fast and slow inactivation. To mimic electrophysiological conditions we induced fast depolarization of toxin-bound synaptosomes, which generated a biphasic unbinding of Lqh-II from toxin-receptor complexes. The first fast off rate closely resembled values determined electrophysiologically for rBII in mammalian cells. The second off rate was similar to the voltage-independent steady-state value, attributed to binding to the slow-inactivated channel states. Thus, the Lqh-II voltage-dependent affinity highlights two independent mechanisms representing conformational changes of sodium channels associated with transitions among electrically visible and invisible inactivated states.

Structural implications on the interaction of scorpion alpha-like toxins with the sodium channel receptor site inferred from toxin iodination and pH-dependent binding

The alpha-like toxin from the venom of the scorpion Leiurus quinquestriatus hebraeus (Lqh III) binds with high affinity to receptor site 3 on insect sodium channels but does not bind to rat brain synaptosomes. The binding affinity of Lqh III to cockroach neuronal membranes was fivefold higher at pH 6.5 than at pH 7.5. This correlated with an increase in the electropositive charge on the toxin surface resulting from protonation of its four histidines. Radioiodination of Tyr(14) of Lqh III abolished its binding to locust but not cockroach sodium channels, whereas the noniodinated toxin bound equally well to both neuronal preparations. Radioiodination of Tyr(10) or Tyr(21) of the structurally similar alpha-toxin from L. quinquestriatus hebraeus (LqhalphaIT), as well as their substitution by phenylalanine, had only minor effects on binding to cockroach neuronal membranes. However, substitution of Tyr(21), but not Tyr(14), by leucine decreased the binding affinity of LqhalphaIT approximately 87-fold. Thus, Tyr(14) is involved in the bioactivity of Lqh III to locust receptor site 3 and is not crucial for the binding of LqhalphaIT to this site. In turn, the aromatic ring of Tyr(21) takes part in the bioactivity of LqhalphaIT to insects. These results highlight subtle architectural variations between locust and cockroach receptor site 3, in addition to previous results demonstrating the competence of Lqh III to differentiate between insect and mammalian sodium channel subtypes.

Scorpion alpha and alpha-like toxins differentially interact with sodium channels in mammalian CNS and periphery

Scorpion alpha-toxins from Leiurus quinquestriatus hebraeus, LqhII and LqhIII, are similarly toxic to mice when administered by a subcutaneous route, but in mouse brain LqhII is 25-fold more toxic. Examination of the two toxins effects in central nervous system (CNS), peripheral preparations and expressed sodium channels revealed the basis for their differential toxicity. In rat brain synaptosomes, LqhII binds with high affinity, whereas LqhIII competes only at high concentration for LqhII-binding sites in a voltage-dependent manner. LqhII strongly inhibits sodium current inactivation of brain rBII subtype expressed in HEK293 cells, whereas LqhIII is weakly active at 2 microM, suggesting that LqhIII affects sodium channel subtypes other than rBII in the brain. In the periphery, both toxins inhibit tetrodotoxin-sensitive sodium current inactivation in dorsal root ganglion neurons, and are strongly active directly on the muscle and on expressed muI channels. Only LqhII, however, induced repetitive end-plate potentials in mouse phrenic nerve-hemidiaphragm muscle preparation by direct effect on the motor nerve. Thus, rBII and sodium channel subtypes expressed in peripheral nervous system (PNS) serve as the main targets for LqhII but are mostly not sensitive to LqhIII. Toxicity of both toxins in periphery may be attributed to the direct effect on muscle. Our data elucidate, for the first time, how different toxins affect mammalian central and peripheral excitable cells, and reveal unexpected subtype specificity of toxins that interact with receptor site 3.

A scorpion alpha-like toxin that is active on insects and mammals reveals an unexpected specificity and distribution of sodium channel subtypes in rat brain neurons

Several scorpion toxins have been shown to exert their neurotoxic effects by a direct interaction with voltage-dependent sodium channels. Both classical scorpion alpha-toxins such as Lqh II from Leiurus quiquestratus hebraeus and alpha-like toxins as toxin III from the same scorpion (Lqh III) competitively interact for binding on receptor site 3 of insect sodium channels. Conversely, Lqh III, which is highly toxic in mammalian brain, reveals no specific binding to sodium channels of rat brain synaptosomes and displaces the binding of Lqh II only at high concentration. The contrast between the low-affinity interaction and the high toxicity of Lqh III indicates that Lqh III binding sites distinct from those present in synaptosomes must exist in the brain. In agreement, electrophysiological experiments performed on acute rat hippocampal slices revealed that Lqh III strongly affects the inactivation of voltage-gated sodium channels recorded either in current or voltage clamp, whereas Lqh II had weak, or no, effects. In contrast, Lqh III had no effect on cultured embryonic chick central neurons and on sodium channels from rat brain IIA and beta1 subunits reconstituted in Xenopus oocytes, whereas sea anemone toxin ATXII and Lqh II were very active. These data indicate that the alpha-like toxin Lqh III displays a surprising subtype specificity, reveals the presence of a new, distinct sodium channel insensitive to Lqh II, and highlights the differences in distribution of channel expression in the CNS. This toxin may constitute a valuable tool for the investigation of mammalian brain function.

Scorpion alpha-like toxins, toxic to both mammals and insects, differentially interact with receptor site 3 on voltage-gated sodium channels in mammals and insects

alpha-Like toxins, a unique group designated among the scorpion alpha-toxin class that inhibit sodium channel inactivation, are highly toxic to mice but do not compete for alpha-toxin binding to receptor site 3 on rat brain sodium channels. We analysed the sequence of a new alpha-like toxin, which was also highly active on insects, and studied its action and binding on both mammalian and insect sodium channels. Action of the alpha-like toxin on isolated cockroach axon is similar to that of an alpha-toxin, and the radioactive toxin binds with a high affinity to insect sodium channels. Other sodium channel neurotoxins interact competitively or allosterically with the insect alpha-like toxin receptor site, similarly to alpha-toxins, suggesting that the alpha-like toxin receptor site is closely related to receptor site 3. Conversely, on rat brain sodium channels, specific binding of 125I-alpha-like toxin could not be detected, although at high concentration it inhibits sodium current inactivation on rat brain sodium channels. The difficulty in measuring binding to rat brain channels may be attributed to low-affinity binding due to the acidic properties of the alpha-like toxins that also impair the interaction with receptor site 3. The results suggest that alpha-like toxins bind to a distinct receptor site on sodium channels that is differentially related to receptor site 3 on mammalian and insect sodium channels.

The putative bioactive surface of insect-selective scorpion excitatory neurotoxins

Scorpion neurotoxins of the excitatory group show total specificity for insects and serve as invaluable probes for insect sodium channels. However, despite their significance and potential for application in insect-pest control, the structural basis for their bioactivity is still unknown. We isolated, characterized, and expressed an atypically long excitatory toxin, Bj-xtrIT, whose bioactive features resembled those of classical excitatory toxins, despite only 49% sequence identity. With the objective of clarifying the toxic site of this unique pharmacological group, Bj-xtrIT was employed in a genetic approach using point mutagenesis and biological and structural assays of the mutant products. A primary target for modification was the structurally unique C-terminal region. Sequential deletions of C-terminal residues suggested an inevitable significance of Ile73 and Ile74 for toxicity. Based on the bioactive role of the C-terminal region and a comparison of Bj-xtrIT with a Bj-xtrIT-based model of a classical excitatory toxin, AaHIT, a conserved surface comprising the C terminus is suggested to form the site of recognition with the sodium channel receptor.

NMR structures and activity of a novel alpha-like toxin from the scorpion Leiurus quinquestriatus hebraeus

NMR structures of a new toxin from the scorpion Leiurus quinquestriatus hebraeus (Lqh III) have been investigated in conjunction with its pharmacological properties. This toxin is proposed to belong to a new group of scorpion toxins, the alpha-like toxins that target voltage-gated sodium channels with specific properties compared with the classical alpha-scorpion toxins. Electrophysiological analysis showed that Lqh III inhibits a sodium current inactivation in the cockroach axon, but induces in addition a resting depolarization due to a slowly decaying tail current atypical to other alpha-toxin action. Binding studies indicated that radiolabeled Lqh III binds with a high degree of affinity (Ki=2.2 nM) on cockroach sodium channels and that the alpha-toxin from L quinquestriatus hebraeus highly active on insects (LqhalphaIT) and alpha-like toxins compete at low concentration for its receptor binding site, suggesting that the alpha-like toxin receptor site is partially overlapping with the receptor site 3. Conversely, in rat brain, Lqh III competes for binding of the most potent anti-mammal alpha-toxin from Androctonus australis Hector venom (AaH II) only at very high concentration. The NMR structures were used for the scrutiny of the similarities and differences with representative scorpion alpha-toxins targeting the voltage-gated sodium channels of either mammals or insects. Three turn regions involved in the functional binding site of the anti-insect LqhalphaIT toxin reveal significant differences in the Lqh III structure. The electrostatic charge distribution in the Lqh III toxin is also surprisingly different when compared with the anti-mammal alpha-toxin AaH II. Similarities in the electrostatic charge distribution are, however, recognized between alpha-toxins highly active on insects and the alpha-like toxin Lqh III. This affords additional important elements to the definition of the new alpha-like group of scorpion toxins and the mammal versus insect scorpion toxin selectivities.

delta-Atracotoxins from australian funnel-web spiders compete with scorpion alpha-toxin binding but differentially modulate alkaloid toxin activation of voltage-gated sodium channels

delta-Atracotoxins from the venom of Australian funnel-web spiders are a unique group of peptide toxins that slow sodium current inactivation in a manner similar to scorpion alpha-toxins. To analyze their interaction with known sodium channel neurotoxin receptor sites, we studied their effect on [3H]batrachotoxin and 125I-Lqh II (where Lqh is alpha-toxin II from the venom of the scorpion Leiurus quinquestriatus hebraeus) binding and on alkaloid toxin-stimulated 22Na+ uptake in rat brain synaptosomes. delta-Atracotoxins significantly increased [3H]batrachotoxin binding yet decreased maximal batrachotoxin-activated 22Na+ uptake by 70-80%, the latter in marked contrast to the effect of scorpion alpha-toxins. Unlike the inhibition of batrachotoxin-activated 22Na+ uptake, delta-atracotoxins increased veratridine-stimulated 22Na+ uptake by converting veratridine from a partial to a full agonist, analogous to scorpion alpha-toxins. Hence, delta-atracotoxins are able to differentiate between the open state of the sodium channel stabilized by batrachotoxin and veratridine and suggest a distinct sub-conductance state stabilized by delta-atracotoxins. Despite these actions, low concentrations of delta-atracotoxins completely inhibited the binding of the scorpion alpha-toxin, 125I-Lqh II, indicating that they bind to similar, or partially overlapping, receptor sites. The apparent uncoupling between the increase in binding but inhibition of the effect of batrachotoxin induced by delta-atracotoxins suggests that the binding and action of certain alkaloid toxins may represent at least two distinguishable steps. These results further contribute to the understanding of the complex dynamic interactions between neurotoxin receptor site areas related to sodium channel gating.

Differences between the electronic environments of reduced and oxidized Escherichia coli DsbA inferred from heteronuclear magnetic resonance spectroscopy

DsbA is the strongest protein disulfide oxidant yet known and is involved in catalyzing protein folding in the bacterial periplasm. Its strong oxidizing power has been attributed to the lowered pKa of its reactive active site cysteine and to the difference in thermodynamic stability between the oxidized and the reduced form. However, no structural data are available for the reduced state. Therefore, an NMR study of DsbA in its two redox states was undertaken. We report here the backbone 1HN, 15N, 13C(alpha) 13CO, 1H(alpha), and 13Cbeta NMR assignments for both oxidized and reduced Escherichia coli DsbA (189 residues). Ninety-nine percent of the frequencies were assigned using a combination of triple (1H-13C-15N) and double resonance (1H-15N or 1H-13C) experiments. Secondary structures were established using the CSI (Chemical Shift Index) method, NOE connectivity patterns, 3(J)H(N)H(alpha) and amide proton exchange data. Comparison of chemical shifts for both forms reveals four regions of the protein, which undergo some changes in the electronic environment. These regions are around the active site (residues 26 to 43), around His60 and Pro 151, and also around Gln97. Both the number and the amplitude of observed chemical shift variations are more substantial in DsbA than in E. coli thioredoxin. Large 13C(alpha) chemical shift variations for residues of the active site and residues Phe28, Tyr34, Phe36, Ile42, Ser43, and Lys98 suggest that the backbone conformation of these residues is affected upon reduction.

Secondary structure of the DNA-binding domain of the c-Myb oncoprotein in solution. A multidimensional double and triple heteronuclear NMR study

The DNA-binding domain of the c-Myb oncoprotein contains two repeats, R2 and R3, both of which have been proposed to be related to the helix-turn-helix (HTH) motif. As a first step towards determination of the three-dimensional structure of this domain and of the mode of interaction with the DNA, we have undertaken multidimensional heteronuclear NMR studies using uniformly 15N-labeled and 13C, 15N double-labeled R2R3 and, a selectively 15N-enriched sample on all lysine, histidine and leucine residues of R2R3. We present almost complete assignments of the backbone 1H, 15N and 13C" atoms and determine the secondary structure of R2R3 in solution. The R3 repeat is composed of three helices (residues 62-75, 78-85 and 91-100) while for the R2 repeat only two helices are found (residues 10-23 and 28-34). The remaining C-terminal part of the R2 repeat, predicted to be helical and part of the HTH motif, undergoes intermediate conformational exchange processes. Stabilization of this segment might occur upon binding to DNA.